Unofficial* summary of the Long Baseline Neutrino Experiment (LBNE)

physics workshopSeattle, Aug 9 to Aug 11

David WebberAugust 24, 2010

*Many studies/plots are preliminary. These slides are a representation of the workshop’s discussion. An official report is in preparation by the collab.

Why Study Neutrinos?

• Neutrinos are half the known stable particles in the universe– n1, n2, n3, p, e, g

• Neutrinos are a major component of the universe– ~300 n/cm3, roughly same as CMB photons– nucleons and electrons are ~10-7/cm3

• Neutrinos allow for the study of particle physics, without the complications of strong and electromagnetic forces.

Svoboda

Neutrino Physics Goals

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neutrino

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Far Detector Options

Water• 100 kT fiducial module.• 4850 ft depth.• 15% or 30% HQE PMT

coverage?• Gadolineum or not?• 1,2,3 modules?• More signal!– Larger volume

Liquid Argon• 17 kT fiducial module.• 300, 800, 4850 ft depth?• 3, 4, 5 mm wire spacing?– Probably will be 3 mm

• photon trigger?• 1,2,3 modules?• Less background!– Better p0 identification

100 kT water ~= 17 kT liquid Ar for beam physics sensitivity

Far Detector Configurations

Long Baseline Physics:CP violation and neutrino hierarchy

Svoboda300 kT water ~= 50 kT liquid Ar for beam physics sensitivity

LBNE could push to 3-4 x 10-3

(see talk by Zeller)

Svoboda

Proton Decay

Svoboda

Galactic Supernova Burst

Scholberg

Neutrino hierarchy determination from a galactic supernova burst

David WebberAugust 20, 2010

H. Duan and A. Friedland, http://arxiv.org/abs/1006.2359

Neutrino energies at infinity(1 second late-time slice of 10-second burst spectrum)

Consider 3 detector possibilities

• Water Cherenkov (WC) with 30% phototube coverage and high quantum-efficiency tubes– This is roughly equivalent to Super-K’s coverage

• WC, 15% coverage, HQE• Liquid Argon

n reaction cross-sections

https://wiki.bnl.gov/dusel/index.php/Event_Rate_Calculations

nepe nDominant reaction:

Water Argon

Dominant reaction:KeAr 40-40 en

Normal Hierarchy: Observed Spectra(accounts for detector acceptance)

WC 30% coverage

n flux at detector

WC 15% coverage Liquid Ar

Inverted Hierarchy: Observed Spectra(accounts for detector acceptance)

WC 30% coverage

n flux at detector

WC 15% coverage Liquid Ar

How many events are needed to distinguish normal from inverted hierarchy in water?

Normal Hierarchy Inverted Hierarchy

102 eventsindistinguishable

•Water Detector•30% PMT coverage•HQE tubes•IBD reaction•c2 shown for “wrong” fit

105 eventsclearly distinguishable

How many events for 3 sigma exclusion?

• Note: c2 is not the same as Gaussian• “3 sigma” = 99.73% confidence• 99.73% confidence is…– c2/NDF of 1.6 for 57 degrees of freedom– c2/NDF of 1.8 for 34 degrees of freedom

c2 vs. events, WC, 30% coverage

Normalhierarchy

Invertedhierarchy

Normal fit Inverted fit

•Water Detector•30% PMT coverage•HQE tubes•IBD reaction ~103.5-3.6 = 3200-4000 events are needed

c2 vs. events, WC, 15% coverage

Normalhierarchy

Invertedhierarchy

Normal fit Inverted fit

•Water Detector•15% PMT coverage•HQE tubes•IBD reaction ~103.5-3.6 = 3200-4000 events are needed

How many events are needed to distinguish normal from inverted hierarchy in argon?

Normal Hierarchy Inverted Hierarchy

102 eventsindistinguishable

105 eventsclearly distinguishable

•Liquid Argon•c2 shown for “wrong” fit

c2 vs. events, liquid argon

Normalhierarchy

Invertedhierarchy

Normal fit Inverted fit

~102.7-2.8 = 500-630 events are needed

Normal and inverted hierarchy neutrino spectra for 99.7% confidence.

Normal Hierarchy Inverted Hierarchy

Liquid Argon630 events

Water Cherenkov30% PMT coverage4000 events

Summary• WC phototube coverage has little impact on resolving the

hierarchy.– 15% is as good as 30%

• To resolve the hierarchy…– ~4000 events must be observed in water, or– ~630 events must be observed in argon

• If a SNB occurs at 8.5 kpc…– Need 18.3 kT water– Need 7.6 kT Ar– a 100kT water module would have better statistics than a 17 kT LAr

module– The LAr module would show more interesting spectral features

Volume estimates based on http://arxiv.org/abs/astro-ph/0701081This study was based on repository revision 754

Confidence vs. Events

See other slides

SNB Hierarchy study improvements:• Allow more parameters to fit in my study to allow for spectral shifts and broadening, eg. E --> E_0 + m*E• Perform a multi-module simultaneous for Argon (nue) and Water (nuebar).

LBNE Workshop Summary

• Choice of far detector is currently undecided– There are many choices

• Liquid Argon has not been attempted at this size– possibility for something new– technical risk

• Details of each detector are still under consideration

Far Detector Options

Water• 100 kT fiducial module.• 4850 ft depth.• 15% or 30% HQE PMT

coverage?• Gadolineum or not?• 1,2,3 modules?• More signal!– Larger volume

Liquid Argon• 17 kT fiducial module.• 300, 800, 4850 ft depth?• 3, 4, 5 mm wire spacing?– Probably will be 3 mm

• photon trigger?• 1,2,3 modules?• Less background!– Better p0 identification

100 kT water ~= 17 kT liquid Ar for beam physics sensitivity

References

• http://www.int.washington.edu/talks/WorkShops/int_10_2b/, Aug 9-10